To powerfully impact the design and success of behavioral weight-management intervention trials that drive the field of obesity treatment, we propose two significant advances. First, we set a new metric for successful weight loss maintenance that is both clinically and behaviorally meaningful-the proportion of individuals who lose =7 percent of initial weight and keep their weight stable over time, i.e., do not gain more than a few pounds after losing weight. Using this demanding metric to interpret trial results forces us to focus on stabilizing each individual's weight trajectory over time and on sustaining stable patterns of lifestyle habits. Second, we contend that an essential motivational construct has been neglected in the adherence-focused weight-management trials to date-whether people actually enjoy engaging in the lifestyle behaviors on a day-to-day basis, regardless of any long-term benefits they may receive. This neglect is problematic as enjoyment is one of the strongest predictors in real-world settings of long-term changes in lifestyle behaviors such as physical activity. Informed by our prior work, this randomized trial will test the real world efficcy and cost-effectiveness of novel modules administered prior to weight loss explicitly designed to enhance enjoyment of lifestyle behaviors independent of any longer-term health effects, and thus substantially escalate the proportion of individuals sustaining =7 percent weight loss over the long-term. Overweight/obese individuals with prehypertension will be randomized to one of two 12-month weight-management interventions (Enjoyment Modules First or Weight Watchers) and followed 24 months after intervention contact ends. This application has two specific aims, each integrating an innovative statistical approach: Aim 1: Test whether Enjoyment Modules First is more efficacious than Weight Watchers. We seek to triple the proportion of overweight/obese adults who achieve the new metric-from 15 percent to 45 percent. We will conduct four field experiments designed to maximize the potency of individual 'prep' modules on the posited mediator of enjoyment for four key lifestyle habits (weighing, nutrition, activity, and self-nurturing); streamline the modules; and test their synergistic potency in the intervention tril. For the primary aim, we will test a fixed effects mediator-intervention interaction model with sufficient a priori power for the interaction. Aim 2: Test whether Enjoyment Modules First is more cost effective than Weight Watchers. To address limitations in prior cost-effectiveness analyses, we will use agent-based modeling, a novel systems science modeling approach to integrate rich individual-level weight-trajectory data from the proposed trial with numerous national-level CVD data sets to produce estimates of the effect of our two interventions on long- term, population-level hypertension and cardiovascular disease incidence, health care and disability costs, and quality-adjusted life-years among different affected US subpopulations over the life course.